The present invention relates in general to the modification of a digital image using a modification tool such as a color or contrast look-up table (LUT).
When using traditional color modification LUTs, color values are adjusted by creating and manually dragging specific control points or xe2x80x9cknotsxe2x80x9d on an input/output LUT graph until the desired color values are produced. Heretofore, the creation and manipulation of a knot on a LUT graph has required multiple steps including the measurement of a color value to be modified, the initialization (e.g., placement) of the knot on the LUT graph at a point corresponding to the measured color value, and the displacement of the knot to modify the measured color value by manipulating the input/output relationship of the LUT graph. Various embodiments of this multi-step process have used in the prior art with limited success. For example, in a first embodiment, a user measures a color value on a digital image using a known method, then defines, through trial and error, a knot on the LUT graph that will best affect the color value of interest. The knot is then manipulated to vary the input/output relationship of the LUT graph. In a second embodiment, the user samples a color in a digital image using a pointer, and a tick mark representing the sampled color appears on the LUT graph. The user then positions a knot as accurately as possible on the tick mark, and manipulates the knot to adjust the color value of interest. In yet another prior art embodiment, the user selects a color value from the digital image, and a knot representing the selected color value automatically appears on the LUT graph. The LUT graph is subsequently manipulated through a manual displacement of the knot.
The present invention provides a simplified method for selecting a color value on a digital image, initializing a color modification tool to the selected color value, and then modifying the color value.
After selecting a color modification tool such as a contrast LUT, the user selects a region on a digital image containing the color value to be adjusted. The selected region is highlighted, and a knot corresponding to the selected color value is automatically placed on the input/output LUT graph of the modification tool. In addition, a slide bar or other suitable control mechanism, and a graphic readout (e.g., numeric display) providing the xe2x80x9cbeforexe2x80x9d and xe2x80x9cafterxe2x80x9d values of the selected color value, are superimposed directly on the digital image adjacent the highlighted region. When the slide bar is displaced to modify the selected color value, the digital image, the graphic readout, and the input/output LUT graph of the modification tool are updated, thereby allowing the user to immediately visualize the affect of the color change on the digital image. Thus, a user can accurately modify a color value via the slide bar without having to directly manipulate the position of a knot on the LUT graph of the modification tool. When the user is satisfied with the modification of the color value within the selected region, the slide bar and graphic readout disappear. However, the color change is saved and the selected region remains highlighted, allowing the user to return to that region if additional color changes become necessary.